Hey,

You can't really as they are not sub pages from the current page, sounds like you need to use the "List sub pages from a changeable source" xslt template, then you can list the sub content like this

<!-- Don't change this, but add a 'contentPicker' element to -->
<!-- your macro with an alias named 'source' -->
<xsl:variable name="source" select="/macro/source"/>

<xsl:template match="/">

<!-- The fun starts here -->
<ul>
<xsl:for-each select="umbraco.library:GetXmlNodeById($source)/* [@isDoc and string(umbracoNaviHide) != '1']">
  <li>
    <a href="{umbraco.library:NiceUrl(@id)}">
      <xsl:value-of select="@nodeName"/>
    </a>
  </li>
</xsl:for-each>
</ul>

</xsl:template>

Rich